public class Circle {
    private double radius;

    public void setRadius(double radius) { this.radius = radius; }
    public double getRadius() { return radius; }
    public double calculateArea() { return 3.14 * radius * radius; }
    public double calculateCircumference() { return 2 * 3.14 * radius; }

    public static void main(String[] args) {
        Circle c = new Circle();
        c.setRadius(5);
        System.out.println("半径: " + c.getRadius());
        System.out.println("面积: " + c.calculateArea());
        System.out.println("周长: " + c.calculateCircumference());
    }
}

